A Muslim kindergarten teacher has lunch with school children during a visit by Renate Schmidt, German Minister for Family Affairs, Senior Citizens, Women and Youth, in Berlin in April (John MacDougall/AFP/Getty Images).

It took decades before Western European countries acknowledged that the guest workers of the 1960s and 1970s had stayed and transformed them into countries of immigration. But only recently have European politicians and public opinion leaders talked about the need to focus on the integration of these immigrants and their children.

In 2005, the spotlight on Muslim immigrants and their children intensified with the deadly bombings on July 7 of a London bus and three underground trains by three British-born men of Pakistani descent and one Jamaican-born man. Later that month, Mohammed Bouyeri, born in the Netherlands to Moroccan parents, was sentenced to life in prison without possibility of parole for the November 2004 murder of filmmaker Theo van Gogh.

The October 27 deaths of two teens of North African descent in Clichy-sous-Bois, a suburb of Paris, sparked two weeks of rioting in disadvantaged immigrant communities across France and inspired possible copy-cat incidents in Belgium, Spain, Germany, the Netherlands, Denmark, Greece, and Switzerland. In 2003, France struggled with the issue of Muslim girls wearing headscarves to school before banning them, along with other religious symbols, in 2004.

These events have highlighted the presence of millions of Muslims in Christian Europe, and natives are concerned about whether, if ever, they can coexist.